1. Field of the Invention
The present invention relates to locking valves, and more particularly, to such valves having means which may be used automatically to secure them in desired positions, that is, in open or closed position, in pipe lines such as gas supply pipe lines.
Numerous automatically locking valves have been proposed for such use. These valves have devices which automatically arrest the movable element of the valve whenever it is moved to a closed position so that only an authorized person in possession of the proper key can release the valve element once it has been so arrested. For example, U.S. Pat. No. 2,016,797 teaches a stop lock having a conical plug rotatable over a 360.degree. range. In either of two open positions, 180.degree. from one another, a passageway in the plug is aligned with a passageway of the housing. In either of two closed positions, 180.degree. from one another and 90.degree. from the open positions, the passageway in the plug is not aligned with the passageway in the housing so that the plug occludes the passageway. A pair of recesses are formed on a stem connected to the plug and rotatable therewith. A lock pin is slidably mounted to the housing and is biased toward the stem. The recesses in the stem are arranged so that whenever the plug is in one of its closed positions, one of the recesses will be aligned with the lock pin and the lock pin will enter such recess to arrest the stem and plug. Because the lock pin is recessed within the housing, the lock pin can only be retracted away from the stem to release it by the use of a special key, which is possessed only by authorized persons.
However, the two closed positions of the plug are not differentiated from one another. An unauthorized person might turn the plug to either of its closed positions in an innocent attempt to shut the valve during an emergency. Thus, an authorized person who is called to release the plug after it has been arrested at one of the closed positions will not be able to tell whether the plug is in such position as a result of innocent operation or as a result of tampering. Further, if a tamperer attempts to defeat the locking features of this valve by driving the plug and stem out of the valve housing, the lock pin will bear the full force of such attack.
An alternative form of locking valve is set forth in U.S. Pat. No. 1,275,135. This locking valve also has a plug rotatable between two closed positions and two open positions and a stem which rotates with the plug. Stops on the outside of the housing normally limit the rotation of the stem and plug to a range between a normal closed position and a normal open position. When the stem and plug are in the normal closed position, a spring loaded lock pin slidably carried by the stem enters into a recess in the housing. However, if a tamperer removes the stops on the outside of the housing, he can rotate the stem and plug to an abnormal closed position in which the pin does not engage the recess and he can then rotate the stem and plug back to an open position. Thus, if the external stops on the valve have been defeated, the valve can be closed and opened at will.
U.S. Pat. No. 4,483,366 discloses a locking valve which includes a housing which defines a fluid passageway, a stem bore open to the outside of the housing at one end and a lock bore intersecting the stem bore. The valve also includes an elongated stem having a relatively narrow portion, a relatively wide portion and a circumferential shoulder at the juncture of such portions. The stem has at least one recess in its relatively narrow portion and is coaxially disposed in the stem bore so that the narrow portion of the stem confronts the lock bore and the shoulder of the stem faces towards the open end of the stem bore. A valve element is connected to the stem for movement in conjunction with rotation of the stem between a closed position and an open position. In the preferred embodiment, the valve element is adapted to seat in the stem bore and has a passageway therethrough. In the normal open position the valve element passageway is aligned with the housing fluid passageway to permit fluid communication therethrough. In the normal closed position such fluid communication is prevented. The recess of the stem is arranged so that it is aligned with the lock bore of the housing when the valve element is in one of the aforementioned positions. A sleeve is coaxially mounted in the lock bore so that the sleeve projects into the stem bore adjacent the shoulder of the stem. Thus, the sleeve prevents axial movement of the stem outwardly through the open end of the stem bore. A lock pin is slidably mounted in the bore of the sleeve, and means are provided for blessing the lock pin towards the stem. The lock pin bears on the stem and enters the recess of the stem when such recess is aligned with the lock bore. The lock pin will arrest rotation of the stem and thus of the valve element when one of the recesses of the stem is aligned with the lock bore.
In other embodiments of U.S. Pat. No. 4,483,366, the shape of the recess of the stem is modified for purposes there described.
If an attempt is made to defeat the locking mechanism of the valve by forcibly withdrawing the stem from the housing through the open end of the stem bore, the sleeve will engage the shoulder of the stem. Thus, the sleeve will bear the forces applied to the stem during such an attack and will protect the lock pin from such forces.
Other locking valves are described in the following U.S. Pat. Nos. 359,714; 703,564; 1,231,164; 1,240,734; 1,325,189; 1,696,757; 2,058,951; 3,450,148; 3,540,481; and 3,560,130.